Linq到SQL左轉(zhuǎn)外部聯(lián)接此查詢是否等效于LEFT OUTER加入？//assuming that I have a parameter named 'invoiceId' of type intfrom c in SupportCaseslet invoice = c.Invoices.FirstOrDefault(i=> i.Id == invoiceId)where (invoiceId == 0 || invoice != null) select new {
Id = c.Id
, InvoiceId = invoice == null ? 0 : invoice.Id}
3 回答
森林海
TA貢獻(xiàn)2011條經(jīng)驗(yàn) 獲得超2個(gè)贊
SelectManyDefaultIfEmpty
var query = from c in db.Customers
join o in db.Orders
on c.CustomerID equals o.CustomerID into sr from x in sr.DefaultIfEmpty()
select new {
CustomerID= c.CustomerID, ContactName=c.ContactName,
OrderID = x.OrderID == null ? -1 : x.OrderID};
繁花如伊
TA貢獻(xiàn)2012條經(jīng)驗(yàn) 獲得超12個(gè)贊
您不需要Into語(yǔ)句：
var query =
from customer in dc.Customers
from order in dc.Orders
.Where(o => customer.CustomerId == o.CustomerId)
.DefaultIfEmpty()
select new { Customer = customer, Order = order }
//Order will be null if the left join is null添加回答
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